In an automatic screw machine, an elongated work piece is turned about its longitudinal center axis and a circular cutting tool held laterally adjacent the work piece is advanced radially toward and against the work piece to remove material according to the profile of the cutting tool. With multiple spindles, several cutting tools of different profiles (rough cut progressing to finish cut) will be used sequentially on each work piece as it is indexed between the separate work stations in being formed into the desired end product.
In most situations, the cutting tool is formed from a cylindrical blank of tool steel having a concentrically centered longitudinal mounting bore extended between opposite end faces. The outer surface of the blank is contoured to define generally circumferential ridge and valley areas that in cross section are related to the exact profile of the desired cutting edge. The actual cutting edge on the circular cutting tool is defined at the corner intersection of the blank's (or tool's) peripherial profile and a trailing face extended inwardly therefrom.
As the controlled tolerances of any product formed with a circular cutting tool relates directly to the accuracy of the cutting tool profile and its cutting edge, such must be formed and sharpened accurately as needed.
Typically, tool specialists fabricate the cutting tool blanks to order, as noted, with appropriate and accurate rough to finish cut peripheries; and with a radial slot ground in each tool periphery to expose and define an initial cutting edge. The tool user may further sharpen the initial cutting edge before use, but thereafter most typically will sharpen all new cutting edges as needed because of wear during use. This sharpening is done by removing a pie-shaped portion of the tool blank immediately next to and including the original cutting edge.
Depending on its size and complexity, each cutting tool blank may typically cost the tool user upward of several hundred dollars, necessitating effective tool management. One aspect of effective tool management depends directly on the ability to sharpen the cutting edge accurately and economically, for providing extended tool usage and reduced tool costs.
Different makes of screw machines have different mechanisms for holding the cutting tools, and for locating their cutting edges or orienting their trailing faces therefrom relative to the work piece. The cutting tools for the different makes of screw machines are not interchangeable. The typical tool user further may be operating in a machine shop that has several different makes of screw machines. Tool management is complicated because of this factor, particularly when sharpening such tools.
In field-sharpening the cutting tool, many tool users merely clamp the tool in a vice, and "eyeball" the grinding of the tool's cutting edge. However, this lack of guidance for accurately setting and making a grinding pass provides wasteful and poor tool management: time-wise, tolerance-wise, and material removal-wise.